1. Field of Invention
The present invention relates to an automatic paper-feeding apparatus, and more particularly to a device for paper separating and guiding, which is disposed at the paper inlet of the automatic paper-feeding apparatus for assisting the pickup of paper sheets.
2. Related Art
A paper pickup device is required to be disposed at the paper inlet of an automatic paper-feeding apparatus, for sequentially feeding overlapped paper sheets into the automatic paper-feeding device one by one. Therefore, a mechanism for assisting the paper separating and guiding is required within the paper pickup device, for separating the paper sheets one by one and ensuring them to enter into the paper-feeding apparatus sequentially. Generally, errors in allocating paper sheets include, for example, 1. multi-feed: two or more than two paper sheets are picked up during the paper feeding; 2. miss-feed: no paper sheets are fed due to different thicknesses of paper sheets; 3. paper jam and paper blocked: the paper feeding is interrupted due to different sizes and thicknesses of the paper sheets. In order to ensure the sequent process of printing, photocopy, and scanning to be performed smoothly, the device for paper separating and feeding must be improved, so as to avoid the above mentioned errors.
The mechanism for paper separating and guiding generally feeds a paper sheet on the top of overlapped paper sheets into a multifunctional peripheral (MFP) through the rotation of a paper pickup roller. The paper pickup roller generally has a rugged surface for frictionally driving the paper sheet. On the other aspect, in order to avoid taking along more than one paper sheet due to the friction force, a paper separating device is require to assist the process of pickup and feeding paper sheets. The most common paper separating and feeding methods are: (1) buckle-type paper separating: paper sheets are separated and by the rigidity of the paper sheets themselves; (2) paper separating through a roller: the separating and feeding of paper sheet is achieved by a paper separating roller and a paper pickup roller rotating towards opposite directions; (3) paper separating through a frictional pad: the othe separating and feeding of paper sheet is achieved by difference of the friction coefficient between a frictional pad and the roller.
As shown in FIG. 1, it is a schematic view of a paper separating and guiding device with a frictional pad to separate paper sheets in the prior art. The multi-feed phenomenon is shown in the figure. When the friction force between the paper sheets to be fed 40 is larger than that between a paper sheet 40a to be fed first and a paper pickup roller 10, the paper sheet 40a to be fed first and the other paper sheets to be fed 40b are together fed into the space between the paper pickup roller 10 and the paper separating device 20, thus the phenomenon of multi-feed occurs. The normal force of the paper separating sheet 20 pressing against the paper pickup roller 10 is provided by an elastic element 25, and the elasticity is fixed, thus, it cannot be adjusted timely according to the roughness and thickness of the paper. Therefore, when the thicknesses or types of the paper sheets are different from the default values, the phenomenon of multi-feed easily occurs, and it also occurs when adopting the paper separating and guiding mechanism using a roller. The buckle-type paper separating mechanism is also influenced by the thickness or type of the paper, such that the phenomenon of multi-feed or paper jam occurs.